30results about How to "Avoid Harmonic Pollution" patented technology

The invention belongs to the technical field of frequency converters and provides a four-quadrant frequency converter. According to the four-quadrant frequency converter, a frequency converter is arranged between a power grid and an induction motor; an energy feedback unit is arranged at a direct current (DC) busbar side of the frequency converter; a negative pole end DC- of a direct current busbar on the frequency converter is electrically connected with the DC- of the energy feedback unit; the DC+ on the frequency converter is electrically connected with DC+ of the energy feedback unit; three-phase alternating current output of the energy feedback unit is connected to input sides R, S and T of the frequency converter in parallel; a PE (Protecting Earthing) terminal of the energy feedback unit is reliably connected to the ground; when the busbar voltage of the frequency converter is detected by the energy feedback unit to be up to a set valve, feedback electric energy is converted to power frequency and transferred to the power grid to carry out energy saving regulation. The four-quadrant frequency converter provided by the invention has the advantages that through an external energy feedback device, the electric energy produced by the motor is added to the input end to the frequency converter after feedback and an electric reactor is additionally arranged to avoid the harmonic pollution, so that the power factor is greatly improved and the efficient utilization ratio of the electric energy is realized.

The invention provides a direct-current auxiliary power supply system. The direct-current auxiliary power supply system comprises a high-voltage direct-current bus, a medium-voltage direct-current bus, a low-voltage direct-current bus, a direct-current auxiliary converter and a direct-current charger, wherein the high-voltage direct-current bus, the medium-voltage direct-current bus and the low-voltage direct-current bus are arranged on a rail vehicle; the direct-current auxiliary converter is connected between the high-voltage direct-current bus and the medium-voltage direct-current bus; thedirect-current charger is connected between the medium-voltage direct-current bus and the low-voltage direct-current bus; the high-voltage direct-current bus is connected to a contact net or a third rail and is used for supplying power to a traction motor of the rail vehicle; the direct-current auxiliary converter is used for supplying power to the medium-voltage direct-current bus; the medium-voltage direct-current bus is used for supplying power to each medium-voltage load in the rail vehicle; the direct-current charger is used for supplying power to the low-voltage direct-current bus; eachmedium-voltage load comprises a frequency-variable air conditioner; and the low-voltage direct-current bus is used for supplying power to a 110V-level storage battery of the rail vehicle. The direct-current auxiliary power supply system provided by the invention can effectively reduce the procedures of conversion of electric energy, can reduce electric energy loss, can improve the running efficiency of an auxiliary system, can lower the running cost of the overall auxiliary system and can improve the energy saving effect of the auxiliary system.

The present invention discloses a ship hybrid power propulsion system based on an active front-end frequency conversion technology. The system comprises a speed change generating set, an energy storage device, a transformer, a direct current distribution board, a propulsion motor, a constant voltage and constant frequency inversion module and an energy management system device. The speed change generating set is connected with a first active front-end rectifying device; a voltage regulation module and a second active front-end rectifying device are connected between the energy storage device and the transformer; the propulsion motor is connected with a motor inversion module; and air breakers are employed to connect the energy storage device with the voltage regulation module, to connect the first active front-end rectifying device with the energy storage device, to connect the first active front-end rectifying device with the direct current distribution board and to connect the secondactive front-end rectifying device with the direct current distribution board. The ship hybrid power propulsion system solves harmonic pollution, improves power supply conversion efficiency, improvesthe load rate of the generating set and achieves purposes of energy saving and emission reduction, reduction of cost and improvement of ship safety.

The invention provides a multi-pole coordinated energy saving device of a distributed type power distribution network. The coordinated energy saving device comprises a data acquisition device, a data integration device and a data monitoring device, which are connected in sequence; the problem of reactive power loss, caused by the fact that reactive power compensation of the power distribution network is not enough, is effectively solved; smooth compensation can be realized by adopting flexible and dynamic reactive power adjusting equipment; the compensation efficiency is high and the compensation degree is accurate; the power grid loss is reduced to the greatest extent; a reactive power compensation device is more stable in a reactive power compensation process and the service life of the reactive power compensation device is prolonged; harmonic pollution in the power distribution network can be effectively solved and normal and reliable operation of a power grid is guaranteed; an automation level of the power distribution network is improved; various devices automatically work and manual intervention can be reduced in an operation process of the power distribution network and the labor intensity of technicians is alleviated; furthermore, various parameters in a power grid operation process can also be collected by the coordinated energy saving device, and overhauling work of the technicians is facilitated.

The invention provides a harmonic detection system and a harmonic processing system, and relating to the technical field of new energy power generation. A wind speed analysis module and a new energy unit analysis module are comprised. The wind speed analysis module is used for analyzing acquired wind speed data to acquire the wind speed and the wind speed type, and extracting first harmonic law information and second harmonic law information from a first package module and a second package module according to the wind speed and the wind speed type. The new energy unit analysis module is used for analyzing the information of a new energy unit to acquire the unit type, proportion and capacity, and extracting third harmonic law information from a third package module according to the unit type, proportion and capacity. On the basis that the wind speed condition or the information of the new energy grid-connected unit is known in a future period, harmonic characteristics in the systems canbe acquired in advance.

A distributed generation (DG) system and a micro power grid have great advantages in utilization of clean energy yet also face numerous problems. Detection of an island effect represents the key link in control over the DG system. The island effect refers to a situation when, due to such factors as a fault in the DG system or maintenance and the like, a large power grid is cut off or stops working, grid-connected equipment does not effectively detect a power failure state and disconnect DG equipment from the large power grid but still supplies energy to a local load. A conventional island detection technology can be divided into a passive detection method, an active detection method and a remote detection method. Compared to the prior art, the method provided by the invention has the following advantages: an island event is rapidly, accurately and reliably detected, the defect of a blind area existing by use of the passive method is effectively avoided, at the same time, injection of certain disturbance signals in a power network is unnecessary, the quality of output electric energy of the generation system is improved, and harmonic wave pollution is prevented.

The invention discloses a photoelectrically isolated voltage buffer power supply, which is characterized in that it mainly consists of a control chip U2, a transformer T1, a transformer T2, a diode rectifier U1, an amplifier P, a triode VT1, a triode VT2, a triode VT3, an anode and a diode rectifier The negative output terminal of U1 is connected, and the capacitor C3 is composed of the negative terminal connected to the positive output terminal of the diode rectifier U1. The invention has larger bandwidth, can improve the dynamic response speed of the invention, and makes the start-up speed of the electrostatic precipitator faster.

The invention discloses an EMI filter. The EMI filter is composed of an input capacitor, a transistor and a control circuit. The control signal generated by the control circuit dynamically changes the voltage at the first terminal of the transistor to compensate the voltage on the input capacitor of the switching power supply. Ripple, to get a smooth input current without switching frequency ripple. In order to prevent high-frequency harmonics from flowing into the power grid, causing harmonic pollution, and the technical implementation method of the present invention is simple, using semiconductor devices to filter out switching frequency ripples, which greatly saves space compared with passive devices, and is more suitable for full surface mounting device applications.

The invention discloses an LED drive circuit with output current self-adjustment capability, which comprises a single-phase AC input power supply, a rectifier bridge, a first power switch tube, a second power switch tube, a first power diode, a second power diode, a second power switch tube, and a second power switch tube. An inductor, a first capacitor, a second capacitor, a high-frequency transformer, a first current sampling resistor, a second current sampling resistor, a first voltage sampling resistor, a second voltage sampling resistor, a third voltage sampling resistor, and a fourth voltage sampling resistor , snubber resistor, snubber capacitor, snubber diode, active power factor correction module. The invention proposes a solution to solve the problem that LEDs work in the state of over-rated current for a long time due to the disconnection of parallel branch circuits. With the characteristics of high stability and safety, it is suitable for the control of various LED lighting circuits.

Provided total reactive power Q requested by system is supplied by n pieces of reactive compensation branch. A fixed capacitor is connected to a variable voltage source in one piece of compensation branch to supply 0-Q / n continuous controlled reactive power. Other n-1 pieces of compensation branch connect fixed capacitor to power source to supply fixed reactive powers. System reactive power is continuous controlled from 0-Q by continuous controlling reactive power in first piece of compensation branch and switching to other compensation branches. The capacity Qv of variable voltage source is only 1 / 4n of Q. Switching operation is implemented at time of zero current of all capacitors in n pieces of reactive compensation branch in order to avoid impulsion from electric network. Features are: low cost to realize reactive continuous control for electric network in high voltage, and prolonging service life of capacitor and switches.

The invention discloses an intelligent mixed type high-pressure dynamic reactive compensation device which comprises a compensation cabinet, a temperature controller and a heat dissipation fan. The temperature controller is used for controlling temperature inside the compensation cabinet. The compensation cabinet comprises a filter, a group of capacitors which are connected in parallel and a group of electric reactors which are connected in parallel. The electric reactors are adjustable electric reactors based on magnetic flux. A controller and a compensation control unit are further arranged inside the compensation cabinet. The controller is used for collecting three-phase high-voltage electricity. The compensation control unit comprises a trigger plate, a thyristor module and an insulated gate bipolar translator (IGBT) module. The compensation control unit receives a switching order of the controller, and is used for detecting of system parameters and compensation controlling of putting in and drawing out. The trigger plate adjusts the electric reactors in a double mode through the thyristor module and the IGBT module, a continuous stepless adjustable control mode is achieved, and adjusting range is wide.

The invention discloses a motor starting device and belongs to the technical field of motor starting equipment. The device provided by the invention comprises an inverter controller, an on-line digital detection system and a DSP (digital signal processor), wherein the inverter controller comprises a three-phase inverter bridge, compensation capacitor, reactors and the like; the three-phase inverter bridge is connected with a power receiving busbar of a motor through the three reactors (or transformers); the compensation capacitor is connected with the DC-side of the three-phase inverter bridge; and the on-line digital detection system, the DSP and the inverter controller form a closed-loop system. According to the invention, the starting device can rapidly track and compensate reactive current needed in the starting process of the motor in real time without producing harmonic current, can reduce voltage dip in the starting process of the motor and can shorten the start-up time of the motor.

The invention provides a charging circuit and a control method thereof. The charging circuit only comprises a group of BUCK charging circuit, the number of the devices is small, and the cost of the devices is relatively low. The voltage input of a single bus is still used, and the states of a first selection unit S1 and a first selection unit S2 are controlled by the input according to whether the voltage of the commercial power is in the positive half cycle or the negative half cycle at present, so that whether a positive bus or a negative bus is accessed is determined, the BUCK step-down ratio is low, the stress of a first switch device Q1 is small, the efficiency is high, the electrolysis capacity of the bus does not need to be large, and the cost of the device is lowered. The technical scheme solves the problems in the prior art that the imbalance of positive and negative buses is caused by load dissymmetry of positive and negative buses and input imbalance of PFC positive and negative semi-cycle power is caused, so that the harmonic pollution caused to the power grid is avoided.